A problem with known engines, be they IC engines, hydraulic pumps, compressors and the like, that have pistons moving in cylinders, is that a consequence of the piston being driven from a rotating crank is that there are lateral forces that act cyclically on the walls of the cylinder as the piston goes through one cycle of operation. The presence of these lateral forces places a number of restrictions on the design of the cylinders since they must be designed in such a way as to overcome these problems.